Method and apparatus for handling disconnection between a media gateway and a media gateway controller

ABSTRACT

The present invention relates to a method and apparatus in a Media Gateway (MG) for handling disconnection between the MG and a Media Gateway Controller (MGC). Multilevel requirements are fulfilled by setting different timeout periods for a disconnection timer. On the one hand, if the timeout period of the disconnection timer is not equal to zero, new events that occur during the disconnection are stored. Then, after the connection is recovered, the stored new events are reported to the MGC, so that the data and states in the MG can match those in the MGC after the connection recovery. On the other hand, if the timeout period of the disconnection timer is equal to zero, all active calls are immediately released.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to the field of communications network,and in particular to a method for handing disconnection between a mediagateway and a media gateway controller in an NGN network.

2. Description of Prior Art

An NGN network provides various kinds of services, such as voicecommunications, multimedia communications and mobility, by using theSoftSwitch technology which separates control, bearer and service fromeach other. From the point of view of functionality, a SoftSwitchnetwork may be divided into a service layer, a control layer, atransport layer and an access layer, from the top down. The mainfunctional entity within the control layer is a Media Gateway Controller(MGC), which primarily provides functions such as call control,connection control and protocol handling etc., and further provides theservice layer with an open interface to various kinds of networkresources in the lower layers. The core transport network of thetransport layer is an IP packet network, which provides channels fortransmitting various kinds of signaling and media streams. The mainfunctional entity of the access layer is a Media Gateway (MG), whichconverts other kinds of access formats into Real Time Protocol/Real-timeTransport Control Protocol (RTP/RTCP) streams suitable for transmissionon the IP network.

Between the MGC and the MG, H.248/MGCP protocol is applied, by which theMGC controls the connection, establishment and release of media streamsover the MG.

When connection between the MG and the MGC is broken (i.e., the MGdetects that the MGC that is currently controlling it fails), the MGattempts to contact the next MGC in a preconfigured list stored thereon,by following the actions specified in Section 11.5 and appendix F.3.6 ofH.248. In practice, on the one hand, many telecommunications operatorswish that a call could be held during the course of recovery of theconnection between the MG and the MGC. The MG preferably holds the callduring the course of connection recovery, so that the MGC is able tocheck the state of the call after the connection is recovered. On theother hand, some MGC are not able to perform such check after thecorresponding connections have been recovered. In this case, thetelecommunications operators probably wish not to hold a call during thecourse of connection recovery. However, the existing H.248 protocol cannot satisfy the above requirements.

SUMMARY OF THE INVENTION

In order to overcome the above drawbacks in the prior art, the presentinvention proposes a method and apparatus in the MG for handling thedisconnection between the MG and the MGC.

According to an aspect of the present invention, there is provided amethod in an MG for handling disconnection between the MG and an MGC,comprising steps of: transmitting a disconnection indication message tothe MGC controlling the MG and starting a disconnection timer, when thedisconnection between the MG and the MGC is detected; determining thetimeout period of the disconnection timer; and storing new events thatoccur during the timeout period of the disconnection timer, if it isdetermined that the timeout period of the disconnection timer is notequal to zero.

According to another aspect of the present invention, there is providedan apparatus in an MG for handling disconnection between the MG and anMGC, comprising: a failure detecting means, for detecting the presenceof the connection between the MG and the MGC controlling the MG; atransmitting means, for transmitting a disconnection indication messageto the MGC controlling the MG, when the disconnection between the MG andthe MGC is detected by the failure detecting means; a timer startingmeans, for starting a disconnection timer when the disconnection betweenthe MG and the MGC is detected by the failure detecting means; adetermining means, for determining the timeout period of thedisconnection timer; and a synchronizing means, for storing new eventsthat occur during the timeout period of the disconnection timer, if itis determined that the timeout period of the disconnection timer is notequal to zero.

By means of the method and apparatus according to the present invention,flexible configurations fulfilling various kinds of requirements fromthe telecommunications operators may be achieved and the disconnectionbetween the MG and the MGC may be effectively handled. Therefore, thesystem performance is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the present invention will become apparent, uponreview of the following description in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic diagram showing a method in a MG for handlingdisconnection between the MG and a MGC according to an embodiment of thepresent invention;

FIG. 2 is a block diagram showing an apparatus in a MG for handlingdisconnection between the MG and a MGC according to an embodiment of thepresent invention;

FIG. 3 is a sequence diagram showing a process of handling disconnectionbetween a MG and a MGC according to an embodiment of the presentinvention; and

FIG. 4 is a sequence diagram showing another process of handlingdisconnection between a MG and a MGC according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In order to overcome the drawbacks existing in the prior art solutionsfor handling disconnection between a MG and a MGC as well as to fulfillthe multilevel requirements from the telecommunications operators, thepresent invention proposes a novel method and apparatus in the MG forhandling disconnection between the MG and the MGC. The method andapparatus will now be described in conjunction with FIGS. 1 and 2 indetail.

When the MGC fails, the MG may detect disconnection between the MGitself and the MGC controlling it, by a failure detecting means 201included therein. Then, the MG executes step S101, at which atransmitting means 202 of the MG transmits the MGC that controlled itbefore the failure a disconnection indication to message, such as aServiceChange message with method=Disconnect. In order to restore thecontrol association in the MG after the connection recovery as itsoriginal state before the disconnection, the MG use the User DatagramProtocol (UDP) port in the original control association before thefailure, to transmit the ServiceChange message. Meanwhile, the MG startsa disconnection timer by a timer starting means 203. The timeout periodof the disconnection timer may be preset in the system, and may be setas different according to different requirements from the operators.Therefore, it is necessary for a determining means 204 in the MG toexecute step S102, at which a determination is made as to whether thetimeout period of the disconnection timer is equal to zero.

If the determination means 204 determines that the timeout period of thedisconnection timer is equal to zero, the MG immediately releases allactive calls by its releasing means 205. Specifically, the contexts ofthe active calls are released and the related resources occupied by theactive calls are reset. For fulfilling the operators' requirement not tohold a call when the MGC fails, the timeout period of the disconnectiontimer may be set to zero.

If the determination means 204 determines that the timeout period of thedisconnection timer is not equal to zero, the MG stores correspondingdata by a synchronizing means 206 included therein, so that the data andstates in the MG can match those in the MGC after the connectionrecovery.

Specifically, with respect to new events that occur during thedisconnection between the MG and the MGC, an event detecting means 207in the synchronizing means 206 executes step S104 to detect these newevents. These new events may be off-hook, hanging-up and dialing etc.There may be a plurality of events or only a single event that occur(s)during the disconnection. The MG executes step S105 for each of thedetected new events, at which each new event is stored in a storingmeans 208. The storing means may be a cache so as to improve the accessspeed. For those active calls, the contexts thereof and resourcesoccupied by them are retained.

During the timeout period of the disconnection timer, the MG repeatedlyexecutes steps S104 and S105, until it receives a reply message from theMGC or the disconnection timer expires.

If within the timeout period of the disconnection timer the MG receivesa reply message from the MGC that controlled it before the failure byits receiving means 209 at step S106, which indicates that theconnection between the MG and the MGC is recovered, a timer stoppingmeans 20 a included in the MG then executes step S107 to stop thedisconnection timer. Next, the MG retrieves the stored new events fromits storing means 208, and transmits the stored new events to the MGC byits transmitting means 202 at step S108.

If within the timeout period of the disconnection timer the MG does notreceive a reply message from the MGC that controlled it before thefailure, the disconnection timer expires at step S109, which indicatesthat the connection between the MG and the MGC is still not recovered.Next, the MG deletes the new events stored in the storing means 208 andreleases all active calls by its releasing means 205 at step S10 a.

On the basis of the above method and apparatus, some specific exampleswill be given in conjunction with FIGS. 3 and 4 as follows. It isassumed that a Terminal A (not shown) is a user terminal managed by anMG 1, an MGC 21 controls an MG 1, and an MGC 22 is the next MGC in alist preconfigured for the MG 1.

In FIG. 3, the Terminal A is in voice communication. Then, the MGC 21fails, the failure detecting means 201 in the MG 1 detects theconnection between the MG 1 and the MGC 21 is lost, and the MG 21triggers the transmitting means 202 to transmit the MGC 21 aServiceChange message, with method=Disconnect and udp port=udp port inthe control association before the failure. Next, the MG 1 starts thedisconnection timer T1, and meanwhile transmits the MGC 22 aServiceChange message, with method=Failover and upd port=2944 bydefault.

After the voice communication is completed, the Terminal A is hung up.Then, the event detecting means 207 in the MG 1 detects the hanging-upevent of the Terminal A, and instructs the storing means 208 to storethis event.

Before the disconnection timer T1 expires, the receiving means 209 inthe MG 1 receives a reply message (Transaction Reply) from the MGC 21.Then, the timer stopping means 20 a stops the timer T1, the storingmeans 208 retrieves the new event (i.e., the hanging-up event of theTerminal A) stored therein, and a Notify message is transmitted to theMGC 21 by the transmitting means 202 so that the hanging-up event of theTerminal A is informed. The MGC 21 releases the context of the activecall of the Terminal A after it receives the Notify message, sets thestate of the Terminal A to idle, and instructs the MG 1 to detectwhether an off-hook event occurs at the Terminal A. These may beachieved by transmitting a Subtract, Modify message to the MG 1. In thisway, after the connection recovery, the MG 1 matches the MGC 21 withrespect to the data and states of the Terminal A.

FIG. 4 is a flow diagram showing a case wherein the connection betweenthe MG 1 and the MGC 1 is still not recovered after the disconnectiontimer expires. Until the disconnection timer T1 expires, the steps forthe MG 1 (that is, step 1 to step 4) are the same as those in FIG. 3.FIG. 4 differs from FIG. 3 in that the MG 1 has not received a replymessage from the MGC 21 before the disconnection timer T1 expires.Therefore, once the disconnection timer T1 expires, the MG 1 immediatelydeletes the stored hanging-up event of the Terminal A and releases thecontext of the call of the Terminal A by means of the releasing means205. Thereafter, the MG 1 continues to try to contact MGC 21 and 22.That is, the MG 1 transmits the MGC 21 a ServiceChange message, withmethod=Disconnect and upd port=2944 by default, and meanwhile transmitsthe MGC 22 a ServiceChange message, with method=Failover and updport=2944 by default.

Although several embodiments of the present invention have been shownand described, those skilled in the art should appreciate that variousmodifications and variations can be made to the above embodimentswithout departing from the spirit and scope defined by the appendedclaims and their equivalents.

1. A method in a Media Gateway (MG) for handling disconnection betweenthe MG and a Media Gateway Controller (MGC), comprising steps of: a)transmitting a disconnection indication message to the MGC and startinga disconnection timer, when disconnection between the MG and the MGCcontrolling the MG is detected; b) determining the timeout period of thedisconnection timer; and c) storing new events that occur during thetimeout period of the disconnection timer, if it is determined that thetimeout period of the disconnection timer is not equal to zero.
 2. Themethod according to claim 1, characterized in that, step c) furthercomprises steps of: c1) detecting the new events that occur during thetimeout period of the disconnection timer; and c2) storing the newevents detected in step c1).
 3. The method according to claim 1 or 2,further comprises steps of: d) receiving a reply message from the MGCthat controlled the MG before the failure, during the timeout period ofthe disconnection timer; e) stopping the disconnection timer; and f)transmitting the new events stored in step c2) to the MGC thatcontrolled the MG before the failure.
 4. The method according to any ofclaims 1 to 3, further comprises steps of: g) the disconnection timerexpiring; and h) releasing all active calls and deleting the new eventsstored in step c2).
 5. The method according to any of claims 1 to 4,further comprises a step of: i) releasing all active calls, if thetimeout period of the disconnection timer is equal to zero.
 6. Themethod according to any of claims 1 to 5, characterized in that, in stepa), the MG transmits the disconnection indication message to the MGCthat controlled the MG before the failure, by using the communicationsport through which the MG communicated with the MGC before the failure.7. An apparatus in an MG for handling disconnection between the MG andan MGC, comprising: a failure detecting means, for detecting thepresence of the connection between the MG and the MGC controlling theMG; a transmitting means, for transmitting a disconnection indicationmessage to the MGC controlling the MG, when the disconnection betweenthe MG and the MGC is detected by the failure detecting means; a timerstarting means, for starting a disconnection timer when thedisconnection between the MG and the MGC is detected by the failuredetecting means; a determining means, for determining the timeout periodof the disconnection timer; and a synchronizing means, for storing newevents that occur during the timeout period of the disconnection timer,if it is determined that the timeout period of the disconnection timeris not equal to zero.
 8. The apparatus according to claim 7,characterized in that, the synchronizing means further comprises: aevent detecting means, for detecting the new events that occur duringthe timeout period of the disconnection timer; and a storing means, forstoring the new events detected during the timeout period of thedisconnection timer.
 9. The apparatus according to claim 7 or 8, furthercomprises: a receiving means, for receiving a reply message from the MGCthat controlled the MG before the failure, during the timeout period ofthe disconnection timer; a timer stopping means, for stopping thedisconnection timer; and a transmitting means, for transmitting the newevents stored in the storing to means to the MGC that controlled the MGbefore the failure.
 10. The apparatus according to any of claims 7 to 9,further comprises: a releasing means for releasing all active calls anddeleting the new events stored in the storing means if the disconnectiontimer expires.
 11. The apparatus according to any of claims 7 to 10,characterized in that, the releasing means is further configured torelease all active calls if the timeout period of the disconnectiontimer is equal to zero.
 12. The apparatus according to any of claims 7to 11, characterized in that, the transmitting means transmits thedisconnection indication message to the MGC that controlled the MGbefore the failure, by using the communications port through which theMG communicated with the MGC before the failure.